There are lots of cheap flights out of Seattle right now on YVR Deals. The prices are in Canadian pesos.

• Seattle to various places in Europe in the $500s CAD roundtrip | spring and fall travel, but also some in August and over Christmas
• Seattle to Geneva, Switzerland - $485 CAD roundtrip including taxes | August dates available
• Seattle to Amsterdam, Netherlands - $485 CAD roundtrip including taxes | May and June 2018
• Seattle to Cologne, Germany - $582 CAD roundtrip including taxes | non-stop flights in August
• Seattle to Rome, Italy (and many other cities in Europe) - $514 to $575 CAD roundtrip including taxes | off-season flights